Journal of Microbiology

2 "Haemophilus influenzae Rd"

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Characteristics of Na^+ -dependent Serine Transport in Haemophilus Influenzae Rd: Young-Mog Kim , In-Koo Rhee , Mi-Yeon Park , Dong-Suck Chang , Tomofusa Tsuchiya; J. Microbiol. 2003;41(2):78-82.

Abstract: We identified two proteins in Haemophilus influenzae Rd that exhibited high similarity to two major serine transporters of Escherichia coli (SstT and SdaC). Then, we investigated serine transport in H. influenzae Rd and detected Na + -stimulated L-serine transport activity. The optimum NaCl concentration for this stimulation was about 20 mM. The uptake of Na^+ by H. influenzae Rd was found to be elicited by L-serine influx, which supports the idea that L-serine is transported by a mechanism of Na^+ / serine symport. No uptake of H + elicited by L-serine influx was detected. Na^+ /serine symport activity was not inhibited by other amino acids such as L-threonine or D-serine. Two distinct Km values were obtained from the kinetic analysis of serine transport. Thus, two serine transport pathways may exist in H. influenzae Rd, and it appears that both systems are stimulated by Na^+ .

Cloning of the Gene for Na+/Serine-Threonine Symporter (sstT) from Haemophilus influenzae Rd and Characteristics of the Transporter: Young-Mog Kim; J. Microbiol. 2003;41(3):202-206.

Abstract: A protein, exhibiting a high similarity to the major serine transporter of Escherichia coli, SstT, was found in Haemophilus influenzae Rd. A Na+-stimulated serine transport activity was also detected in the cells. The gene (sstT) for the Na^+/serine symporter from the chromosome of H. influenzae was cloned, and the properties of the transporter investigated. The serine transport activity was stimulated by Na^+. The uptake of Na^+ was elicited by the addition of serine or threonine into the cells, supporting the idea that these amino acids are transported by a mechanism of Na^+/substrate symport. No uptake of H^+ was elicited by the influx of serine. The serine transport via the SstT of H. influenzae was inhibited by excess threonine, which was used as another substrate. The K_m and the V_max values for the serine transport were 2.5 mM and 14 nmol/min/mg protein, respectively.

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